This invention relates to removing toner and other residue from the photosensitive drum in an electrophotographic apparatus by means of a cleaning blade consisting of a rigid holder coupled with an elastic wiper. The edge of the elastic wiper is caused to bear against the surface of the photosensitive drum, thus wiping toner and other residue off the drum as it rotates.
Two popular types of cleaning blades are distinguished by the method of forming and attaching an elastic wiper, usually polyurethane, to a rigid holder typically made of stamped steel sheet or extruded aluminum. The first type of cleaning blade is molded whereby liquid polyurethane is introduced into a mold with the rigid holder affixed therein. The assembly is oven cured to obtain the desired physical characteristics of the urethane, which is then precision trimmed to form the surface to be placed in contact with the rotating drum. The second type of cleaning blade is fabricated by attaching a polyurethane strip cut from a preformed sheet to the rigid holder using an adhesive, preferably double-sided adhesive tape.
In the family of electrophotographic apparatus, which includes copy machinery and laser printers, the diversity of geometries have spawned the development of approximately four hundred and fifty different cleaning blade configurations. The design of these systems has typically not considered the use of standardized cleaning blade configurations in different applications, leading to this proliferation of cleaning blade configurations.
In the prior art, the cleaning blades are specifically designed for a particular application without regard to using a standardized cleaning blade configuration interchangeably in different electrophotographic machines. Currently, there are no means available to locate and secure a standard configuration cleaning blade to preserve its geometric relationship with the photosensitive drum for different machines, nor to allow for interchangeability of a standard cleaning blade in different machines.
In the prior art, the cleaning blade is attached directly to a mounting area integral to the particular electrophotographic apparatus, normally using screws to secure the cleaning blade in position. Note that hereafter in this specification this mounting area described will be referred to as a “primary mounting” or alternatively as a “cleaning blade mount.” The primary mounting often has ears, tabs, or other locating provisions, which cooperate with notches on one or both ends of a blade holder to locate the cleaning blade with respect to the photosensitive drum. Thus, for each apparatus, a uniform pressure, contact area, and contact angle of the wiper is maintained relative to the photosensitive drum.
Examples of prior art cleaning blades are shown in FIGS. 1 and 2 of the accompanying drawings. The cleaning blades (collectively 1A and 2A or 1B and 2B) are attached directly to a primary mounting 4, the geometry of which is dependant upon the particular machine design, to maintain a desired pressure, contact area, and geometric relationship, primarily parallelism, of the elastic wiper to the photosensitive drum being cleaned. FIG. 1 illustrates an example of a cleaning blade with an elastic wiper blade 2A molded onto a holder 1A, the blade having a flat surface abutting the surface of the photosensitive drum 3 to be cleaned and a sloped (or tapered) surface on the side opposite from the flat surface. FIG. 2 illustrates an example of a cleaning blade with an elastic wiper blade 2B of rectangular cross-section adhesively affixed to a holder 1B.
The cleaning blades shown in FIGS. 1 and 2 are mounted so the edge of the elastic wiper bears against the photosensitive drum in opposed relationship with the movement thereof (i.e. in the direction of the arrow) to remove toner and other residue. It should be noted that the cleaning blades of FIGS. 1 and 2 are not reversible and cannot be selectively mounted so that either opposite edges of the wiper blades clean the drum.
A disadvantage of the prior art is that the configurations of the various cleaning blades are very specific because they are designed only to mate with corresponding cleaning blade mounts without any regard for standardization or interchangeability. In other words, the prior art does not disclose or even suggest using a common cleaning blade configuration for different or multiple applications since the prior art does not teach or suggest any uniform means for locating and stabilizing the cleaning blade to preserve its geometric relationship to the photosensitive drum for differing cleaning blade mount configurations.
Moreover, the design and manufacture of prior art cleaning blades prevents their wiper blades from being reused in the event of a worn or defective wiper blade. The molded wiper blades cannot be removed without damaging them, thus preventing their replacement on a holder, and the adhesive on the adhesively attached wiper blades prohibits their removal and re-use on the rigid holder.
Furthermore, the configuration of the elastic wipers used in prior art are such that the thickness of the elastic wiper at the edge placed in contact with the photosensitive drum is less than or equal to the thickness of the elastic wiper at all points in the direction of the rigid holder. As the edge of the elastic wiper wears down, the contact pressure against the photosensitive drum diminishes, rendering the cleaning blade prematurely ineffective.
This invention overcomes the above-discussed problems and provides a universally usable cleaning blade which is preferably reversible for twice the useful life, and preferably has additional features which make it longer lasting. These advantages and attributes of this invention and others will be readily understood upon a reading of the text hereinafter.